Hα and Hβ emission in a C3.3 solar flare: comparison between observations and simulations

Capparelli, V., Zuccarello, F., Romano, P., Simões, P. J.A. , Fletcher, L. , Kuridze, D., Mathioudakis, M., Keys, P. H., Cauzzi, G. and Carlsson, M. (2017) Hα and Hβ emission in a C3.3 solar flare: comparison between observations and simulations. Astrophysical Journal, 850(1), 36. (doi:10.3847/1538-4357/aa9187)

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Abstract

The Hydrogen Balmer series is a basic radiative loss channel from the flaring solar chromosphere. We report here on the analysis of an extremely rare set of simultaneous observations of a solar flare in the Hα and Hβ lines at high spatial and temporal resolution, which were acquired at the Dunn Solar Telescope. Images of the C3.3 flare (SOL2014-04-22T15:22) made at various wavelengths along the Hα line profile by the Interferometric Bidimensional Spectrometer (IBIS) and in the Hβ with the Rapid Oscillations in the Solar Atmosphere (ROSA) broadband imager are analyzed to obtain the intensity evolution. The Hα and Hβ intensity excesses in three identified flare footpoints are well correlated in time. We examine the ratio of Hα to Hβ flare excess, which was proposed by previous authors as a possible diagnostic of the level of electron beam energy input. In the stronger footpoints, the typical value of the the Hα/Hβ intensity ratio observed is ∼0.4−0.5, in broad agreement with values obtained from a RADYN non-LTE simulation driven by an electron beam with parameters constrained (as far as possible) by observation. The weaker footpoint has a larger Hα/Hβ ratio, again consistent with a RADYN simulation but with a smaller energy flux. The Hα line profiles observed have a less prominent central reversal than is predicted by the RADYN results, but can be brought into agreement if the Hα-emitting material has a filling factor of around 0.2--0.3.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Simoes, Dr Paulo and Fletcher, Professor Lyndsay
Authors: Capparelli, V., Zuccarello, F., Romano, P., Simões, P. J.A., Fletcher, L., Kuridze, D., Mathioudakis, M., Keys, P. H., Cauzzi, G., and Carlsson, M.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Astrophysical Journal
Publisher:IOP Publishing
ISSN:0004-637X
ISSN (Online):1538-4357
Published Online:14 November 2017
Copyright Holders:Copyright © 2017 The Authors
First Published:First published in Astrophysical Journal 850(1):36
Publisher Policy:Reproduced under a Creative Commons License
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
595181Chromospheric Flares: Observations, Models and Archives (CHROMA)Lyndsay FletcherEuropean Commission (EC)606862P&A - PHYSICS & ASTRONOMY
631581Consolidated grant in solar and astrophysical plasmasLyndsay FletcherScience & Technology Facilities Council (STFC)ST/L000741/1S&E P&A - PHYSICS & ASTRONOMY